Industrial fabrication processes are increasingly turning to printing systems to fabricate layers of products. These printing systems deposit a fluid, which is then cured or hardened to form a permanent layer of a particular product. These fabrication processes are especially useful for the fabrication of microelectronic products or products with arrays of quasi-electronic structures. For example, such printing processes are increasingly being used to manufacture thin film electronic displays and solar panels for a wide variety of applications. The mentioned printing systems are typically characterized by, in addition to the type of fluid utilized (“ink”), the use of many thousands of print nozzles on one or more printheads that are designed with capabilities to place individual, substantially uniform size droplets with near micron resolution. This precision control over both deposited droplet volume and position helps facilitate high quality in end-products as well as high-resolution, small footprint products and reduced manufacturing costs. For example, in one application, namely the manufacture of organic light emitting diode (OLED) displays, the ability to precision deposit the inks helps produce smaller, thinner, more resolute displays at lower cost. Note that while the term “ink” is used to refer to the deposited fluid, the deposited fluid is typically colorless, and is deposited as a structure that will “build” a thickness of a permanent layer of a device, i.e., the color of the fluid itself is typically not important in the sense it would be for ink used in a conventional graphics printing application.
Not surprisingly, in these applications, quality control is dependent on uniformity in deposited ink droplets, as to size (droplet volume) and precise position, or at least an understanding as to variation in such features is important to be able to produce permanent layers that consistently meet desired quality standards for layer registration accuracy and/or layer homogeneity. Note that in an industrial printing system, droplet uniformity for any given nozzle can also potentially change over time, whether due to statistical variation, changes in nozzle age, clogging, ink viscosity or constituency variation, temperature, or other factors.
What is needed is a droplet measurement system adapted for use in connection with an industrial printing process, ideally, for in situ use with a printing system used by an industrial fabrication apparatus. Ideally, such a droplet measurement system would provide near fast measurement of one or more droplet parameters, be easy to maintain, and provide inputs that could be used to adjust printing, so as to enable precise quality control for used in the industrial product fabrication processes. The present invention addresses these needs and provides further, related advantages.
The subject matter defined by the enumerated claims may be better understood by referring to the following detailed description, which should be read in conjunction with the accompanying drawings. This description of one or more particular embodiments, set out below to enable one to build and use various implementations of the technology set forth by the claims, is not intended to limit the enumerated claims, but to exemplify their application. Without limiting the foregoing, this disclosure provides several different examples of a droplet measurement system that optically measures or images deposited droplets on a medium, and that uses image processing to identify values of a parameter for various nozzles of a printhead used in industrial fabrication. The various techniques can be embodied as a droplet measurement system, as a printer or fabrication apparatus, or as software for performing described techniques, in the form of a computer, printer or other device running such software, or in the form of an electronic or other device (e.g., a flat panel device or other consumer end product) fabricated as a result of these techniques. While specific examples are presented, the principles described herein may also be applied to other methods, devices and systems as well.